As a projection video display apparatus, an apparatus which includes: a light source; a display element on which light emitted from the light source is incident; and a variable light adjusting function which changes the amount of light incident on the display element has been known. For example, Patent Document 1 discloses an illumination apparatus used in a projection display apparatus, and the illumination apparatus includes: a light source; uniform illumination means which makes the illuminance distribution of light incident from the light source uniform; and light adjusting means which adjusts the amount of light emitted from the light source. Further, Patent Document 1 describes that the amount of light emitted from the uniform illumination means can be adjusted by controlling the light adjusting means based on information from the outside.